The use of coronary vasoactive drugs during coronary arteriography will be further investigated in animals, in an effort to recognize hemodynamic effects of coronary stenoses. Angiograms will be performed with magnification on cut film, which provides unparalleled resolution of fine coronary branches. At the same sitting, cine coronary arteriography will be performed before and after pharmacologic manipulation of peripheral myocardial vascular resistance, in order to most readily recognize relative alterations in linear velocity of flow. The usefulness of pharmacologically provoked spasm in augmenting collateral flow will also be investigated.